Identifying Trend Patterns of Mean Relative Humidity in Isfahan Province

Increased greenhouse gases in the atmosphere not only cause global warming but also cause changes in the behavior of meteorological parameters such as moisture in the air. The purpose of this research is to identify patterns of mean relative humidity in Isfahan in the past half a century. In this regard, the monthly mean relative humidity of 21 stations inside and outside the province during the period of 1961 to 2010 were analyzed. First homogeneity and normality of data were measured. Then station data were arranged in a matrix with the dimensions of 21×600 and the T mode, and were converted into pixel data with dimension of 5×5 square km through programming and interpolation by Kriging method. Then the data that were outside the province area were removed and 4260 pixels remained. In the next stage Mann - Kendall test was used to reach the trend for each pixel and the resulting trends were zoned and analyzed. The results indicate during February to November the decreasing trend covers most of the province, and by contrast, in the months of January and December there is no specific trend to be observed. Studies on the rate of change of relative humidity, confirmed that the greatest reduction in relative humidity happens during the months of February, August, March and April. In general, in the studied period, decreased the average relative humidity of Isfahan Province had decreased to 10/02 %.